Storage locations to stay safe

While efforts are ramping up to rebuild and reinforce lake-size drinking water reservoirs east and south of San Francisco, a blitz of similar work at smaller facilities is well under way inside The City.

The multibillion-dollar Water System Improvement Project aims to protect The City’s drinking-water supply from earthquakes and help the San Francisco Public Utilities Commission catch up on needed maintenance.

The system comprises massive dams and school bus-size pipes east and south of San Francisco that deliver snowmelt from Hetch Hetchy Reservoir in the Sierras and some river water.

Once water reaches The City, it enters a labyrinth of above-ground tanks, subterranean reservoirs, pump stations and narrower piping.

San Franciscans would rely largely on water stored within city limits for a period of time if an earthquake or other disaster ruptured major pipelines that deliver water into The City.

“We have to be self-sufficient,” said Howard Fung, a San Francisco Public Utilities Commission water official overseeing WSIP projects inside city limits. “That’s why these large reservoirs were built following the fire and earthquake in ’06 — we wanted to have storage locally.”

The largest in-city water storage facilities are underground reservoirs that are being refurbished and seismically reinforced under WSIP.

Such work helps protect neighborhoods from floods and increases the likelihood that water will continue flowing through taps if any of the reservoirs are affected by an earthquake.

One of the two subterranean storage basins at the University Mound Reservoir was drained in late July, allowing frantic, floodlit work to begin in 12-hour daily spurts inside the cavernous facility, which is covered by a concrete sheath.

“The other basin had some work done several years ago,” Fung said. “It’s a very old reservoir.”

New columns and struts and diagonal bracing are being installed inside the Portola district reservoir to better protect it from earthquakes. Aging concrete, reservoir lining, inlets, outlets and pipes are also being replaced. Work is expected to cost $47 million and finish in 2011.

A similar project finished earlier this year at one of the two Sunset Reservoir basins, which store water in the outer avenues, and another project is being planned west of Twin Peaks at Sutro Reservoir.

The City’s drinking-water reservoirs are supplemented by scores of above-ground tanks and pump stations that help push water to customers up San Francisco’s hilly terrain.

“The topography of The City isn’t flat, so we couldn’t deliver water from one central location,” Fung said.

Tanks and pump stations are also being reinforced, rebuilt and built anew under WSIP.

Pipeline nourishes both sides of SF

An underground pipeline was laid this year across The City to help ensure that both sides of San Francisco remain quenched following a calamity.

If major pipelines into The City rupture, one or more of San Francisco in-city reservoirs could start drying out as customers draw down its supplies.

The new East/West Transmission Main, which ranges from 36 to 42 inches wide, will allow water officials dealing with desiccating reservoirs to shift supplies between the eastern and western parts of The City.

The 4½-mile pipeline, which was laid as part of the Water Safety Improvement Project at a cost to water ratepayers of $28.6 million, connects the University Mound Reservoir in the Portola district to the Sunset Reservoir.

Existing pipelines were also being dug up and replaced beneath The City under WSIP.

Protecting water delivery

The Water System Improvement Program is a $4.4 billion to $4.6 billion, 12-year effort to rehabilitate and protect the system of pipes, reservoirs and equipment from earthquakes. The entire system delivers water — largely from the Hetch Hetchy Reservoir in Yosemite National Park — to 2.5 million Bay Area customers.

Delivering water

Facts about the water network inside San Francisco city limits:

14.5 Miles of pipeline7 Reservoirs13 Pump stations8 Water storage tanks